As an NTC thermistor or a PTC thermistor used as a temperature sensor or the like in a protection circuit heretofore, one disclosed in Patent Document 1 is known. The thermistor has a plate-like metal substrate which also serves as an electrode, a themosensitive resistor film formed on one surface of the plate-like metal substrate, and an electrode film formed on the themosensitive resistor film.
However, since the thermistor has a structure in which the plate-like metal substrate is used as one electrode and the electrode film formed on the top layer is used as another electrode, there is no choice but to use wire bonding for electrical connection to the electrode film. Therefore, it has been impossible to mount the same on a minimal space. For example, when used as a temperature sensor of IC component mounted on a printed-circuit board, there is a 150 to 200 μm minute space between the printed-circuit board and the IC component, and it is preferable to mount the thermistor in the space. However, the mounting by wire bonding does not allow mounting on such a minimal space.
Moreover, the themosensitive resistor film (thermistor thin film) has been formed by a gas phase method, such as sputtering, in the thermistor, which has caused problems of an increase in the cost and poor productivity. Furthermore, the thermistor has had problems that, when cracking or the like occurs in the metal substrate or the themosensitive resistor film, the resistance has fluctuated to change the characteristics as a temperature sensor.
PTL 1: Japanese Unexamined Patent Application Publication No. 61-245502